Van der Pol oscillator
In the study of dynamical systems, the van der Pol oscillator (named for Dutch physicist Balthasar van der Pol) is a non-conservative, oscillating system with non-linear damping. It evolves in time according to the second-order differential equation d 2 x d t 2 = μ ( 1 − x 2 ) d x d t − x , {\displaystyle {d^{2}x \over dt^{2}}=\mu (1-x^{2}){dx \over dt}-x,} where x is the position coordinate—which is a function of the time t—and μ is a scalar parameter indicating the nonlinearity and the strength of the damping.